According to sources in the Nigerian town of Chibuk, the Boko Haram let go of the four girls, while other sources believed that the girls managed to escape.
The Punch, a local daily newspaper, said the number of freed girls has risen to 75.
Chief of Defence Staff Air Marshal Alex Badeh said earlier that the authorities knew where the abducted girls were, but expressed inability to reveal their whereabouts.
"The good news for the parents of the girls is that we know where they are, but we cannot tell you," Badeh was quoted as saying by The Punch. "We want our girls back, I can tell you that our military can and will do it. But we cannot kill our girls in the name of trying to get them back."
The Boko Haram killed 40 people Wednesday and injured 10 others during an attack in northeastern Nigeria.
The media said the Boko Haram insurgents attacked Ngurmuji, a village in Borno state. They opened fire at the village's residents while setting many houses afire.
The Punch reported that the village was totally destroyed, which led to its inhabitants fleeing into the woods.
The Boko Haram, which was added to the UN's terrorism list in May 2014, seeks to establish an Islamic state ruled by the Sharia law.
The group's attacks have led to the displacement of about 250,000 people in the northern regions of the country and caused the death of over 700 people since the beginning of this year.
Nigeria is the most populous country in Africa with a population of around 170 million, and has more than 200 tribes. The country suffers from multiple tensions for political, social, religious and regional reasons.